|
Arius (fish)
''Arius'' is a genus of catfishes (order Siluriformes) of the family Ariidae. The genus ''Arius'' is distributed in brackish and fresh waters of Eastern Africa and south to Southeast Asia. Defining the limits so that ''Arius'' can form a natural grouping has always been a problem. The genus was never properly defined, and many species previously classified in ''Arius'' are now in other genera. Recent authors have recognized this genus as non monophyetic, rejecting that the genus is a natural grouping. Two unnamed groups are distinguished by accessory tooth plates, which are either very elongated and bearing molar-like teeth, or are oval shaped or subtriangular and bearing acicular (needle-like) or conic teeth. ''A. jatius'' lacks these tooth plates, but has been included in this genus based on its adipose fin and lateral line. The recognition of ''Arenarius'' as a junior synonym of ''Arius'' is tentative and needs to be further investigated. ''Arius'' species have three pairs of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maastrichtian
The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from . The Maastrichtian was preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene). The Cretaceous–Paleogene extinction event (formerly known as the Cretaceous–Tertiary extinction event) occurred at the end of this age. In this mass extinction, many commonly recognized groups such as non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-known groups, died out. The cause of the extinction is most commonly linked to an asteroid about wide colliding with Earth, ending the Cretaceous. Stratigraphic definitions Definition The Maastrichtian was introduced into scientific literature by Belgian geologist André Hubert Dumont in 1849, after studying rock strata of the Chalk Group c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
